Figure 6.

ERK5 icKO mice are compromised in contextual fear extinction. A, Schematic illustration of the standard fear-conditioning paradigm where animals were subjected to one 0.7 mA, 2 s footshock. B, Control and ERK5 icKO mice have similar levels of contextual fear memory 24 h after training. C, Neither control nor ERK5 icKO mice froze when placed in a novel context 24 h after training. D, Control and ERK5 icKO mice showed similar cued-fear response 24 h after training. E, However, fear extinction was impaired in ERK5 icKO mice. Day 0, Day of contextual fear testing; day 1, first day animals were subjected to fear extinction training. F, The freezing response that persisted after fear extinction trials was context specific because animals did not freeze in a novel context on day 9, 1 d after the completion of the fear extinction trials. Data are mean ± SEM from two independent experiments with n ≥ 8 animals per treatment group per experiment. n.s., Not significant. **p < 0.01; ***p < 0.001.